Surveying the Bright Stars by Optical Interferometry I: A Search for Multiplicity Among Stars of Spectral Types F - K

TL;DR

This paper reports on a survey using optical interferometry to detect stellar multiplicity among bright F-K type stars, presenting new binary detections, orbit solutions, and angular diameter measurements, thereby advancing the understanding of stellar companions.

Contribution

It introduces the first results of a NPOI-based survey targeting bright stars, including new binary detections, orbit determinations, and diameter measurements, enhancing previous observational efforts.

Findings

Detected and characterized several known binaries with high precision.

Reported a new orbit solution for sigma Her.

Found no new close companions within detection limits for most stars.

Abstract

We present the first results from an ongoing survey for multiplicity among the bright stars using the Navy Precision Optical Interferometer (NPOI). We first present a summary of NPOI observations of known multiple systems, including the first detection of the companion of $\beta$ Scuti with precise relative astrometry, to illustrate the instrument's detection sensitivity for binaries at magnitude differences $\Delta$$m$ $\lessapprox$ 3 over the range of angular separation 3 - 860 milliarcseconds (mas). A limiting $\Delta$$m_{700}$ $\sim$ 3.5 is likely for binaries where the component spectral types differ by less than two. Model fits to these data show good agreement with published orbits, and we additionally present a new orbit solution for one of these stars, $\sigma$ Her. We then discuss early results of the survey of bright stars at $\delta$ $\geq$ -20$\deg$. This survey, which complements previous surveys of the bright stars by speckle interferometry, initially emphasizes bright stars of spectral types F0 through K2. We report observations of 41 stars of apparent visual magnitude $m_V$ $\leq$ 4.30, all having been observed on multiple nights. Analysis of these data produces fitted angular separations, position angles, and component magnitude differences for six previously known visual binaries. Three additional systems were examined as possible binaries, but no conclusive detection could be made. No evidence of close stellar companions within our detection limit of $\Delta$$m$ $\approx$ 3 was found for the remaining 32 stars observed; however, uniform-disk angular diameters are reported for 11 of the resolved stars in this last group.